Class 12 Biology Chapter 3 Question Answers

Important Terms on Chapter 3

Gestation Period: A period between fertilisation of ovum and the birth of a baby.

Implantation: Fixing of ernbryo/fertilized egg in uterus. It leads to pregnancy.

Menarche: The beginning of first menstruation in female on attaining puberty. Menopause: Permanent ceasation of menstrual cycle in female. It occurs between the age 45 to 50 years in human female.

Puberty: A stage at which immature reproductive system of boy or girl becomes mature. Period of puberty is 10-14 years in girls and 13-16 years in boys.

Ovulation: Process of release of mature ovum (Secondary oocyte) from the ovary.

Parturition: Process of delivery of the foetus (Child birth), through birth canal.

Spermiogenesis: Transformation of spermatids into sperms.

Spermiation: A process by which spermatozoa are released from the seminiferous tubules.

Spermatogenesis: Process of formation of sperm from male germ cell in the testes.

Lactation: The fluid secreted by mammary glands soon after birth is called colostrum. It contains proteins, lactose and antibodies (e.g. IgA). This provides nutrition and help the new born baby to develop resistance for healthy development.

Questions for revision

Failure of testes to descend into sacrotal sacs leads to sterility. Why?

How many sperms will be produced from 10 primary spermatocytes and how many eggs will be produced from 10 primary occytes?

What is meant by L.H. Surge? Write the role of L.H.

T.S. of mammalian testis revealing seminiferous tubules show different types of cell. (i) Name the two types of cells of germinal epithelium. (ii) Name of cells scattered in connective tissue and lying between seminiferous tubules.

Answers

High temperature of abdomen kills the spermatogenic tissue of the testes, so no sperm are formed.